This invention relates in general to impact printers and more particularly to the means for stabilizing the carriage during the printing operation of the printer.
The Diablo Corporation, a subsidiary of the present assignee, is marketing a serial printer under the tradename of Diablo Hytype I which employs a movable carriage with a daisy-type print wheel, print hammer and ribbon cartridge mounted thereon. A printer of this type is disclosed in U.S. Pat. No. 3,954,163 which issued from U.S. patent application, Ser. No. 505,105, which is a continuation of a U.S. patent application filed Sept. 4, 1973, in the name of Andrew Gabor, Ser. No. 394,072, entitled "High Speed Printer and Intermittent Printer Wheel with Carriage Movement", now abandoned, being a continuation of an application filed Feb. 25, 1972, Ser. No. 229,314, now abandoned, the disclosure of which is incorporated by reference into this specification.
The Diablo Hytype I printer is enjoying commercial success as a serial printer in such applications as communication terminals, computer output devices, etc. However, in certain type applications, such as automatic text-editing typewriter applications in the office environment, additional features and capabilities are desired, e.g., higher print quality. In the text-editing or office-typing environment, the demands for high print quality cause the print wheel to be subjected to about ten times greater force due to about five times greater hammer energy compared to a Hytype I printer operating as a computer output terminal, for example. To provide the high print quality needed, the integrally molded thermoplastic print wheel of the Hytype I printer was replaced by a composite print wheel, such as that disclosed in a copending U.S. patent application, Ser. No. 683,977, being a continuation of an application filed Sept. 25, 1974, in the name of Gordon Sohl et al. Ser. No. 509,193, now abandoned. In addition, a different print hammer assembly was incorporated therein which provided greater hammer energy. A card guide was added to the carriage to provide assistance in the operation of inserting and aligning paper in the automatic text- editing typewriter. The noted changes and additions resulted in an increase of the mass of the carriage. One problem with this type of carriage, because of the geometry of the carriage (high mass center of the structure), is the resulting error in the horizontal alignment or positioning of the printed characters on the record medium. The horizontal alignment or positioning of the printed characters on the record medium exceeded the competitive print quality specification by about .+-.0.002 inch in the manual typing mode and about .+-.0.008 inch in the automatic typing mode. The predominate cause of the problem is the movement of the carriage during print time (i.e., when the character slug of the print wheel strikes the platen with reference to the start of hammer fire pulse).
Accordingly, it is a primary object of the present invention to provide an economical method and apparatus for reducing the horizontal alignment error of the printed characters in document creation equipment employing a print wheel impact printer along the presently described vane.
Another object of this invention is to provide a simple and reliable means to reduce the horizontal alignment error of the printed characters, which is compatible with the existing carriage and which may be implemented without significantly increasing the bulk and complexity of the carriage.
Other objects and advantages will be evident from the specification and claims when read in conjunction with the accompanying drawing illustrative of the invention.